We have demonstrated by autoradiography that GnRH and analogs of GnRH are localized intracellularly within one minute following intracarotoid injection. Studies are being conducted to determine if the intracellular localization is due to the presence of intracellular receptors or to internalization of membrane receptors. Secondly, we have proposed to determine if intracellular binding is necessary to evoke release of LH. A second series of studies are being conducted to determine how gonadal steroid hormones mediate release of LH induced by GnRH. In this respect we are determining the effect of gonadal steroids on number of receptors for GnRH in the anterior pituitary, the effect of these steroids on percentage of LH released from dissociated ovine pituitary cells in response to GnRH, and the effects of steroids on half-maximal responsiveness of pituitary cells to GnRH.